Question: Simplify the following expression: $n = \dfrac{r^2 - 7r + 6}{r - 6} $
Explanation: First factor the polynomial in the numerator. $ r^2 - 7r + 6 = (r - 6)(r - 1) $ So we can rewrite the expression as: $n = \dfrac{(r - 6)(r - 1)}{r - 6} $ We can divide the numerator and denominator by $(r - 6)$ on condition that $r \neq 6$ Therefore $n = r - 1; r \neq 6$